Variable fan speed control

[michoujordan76]

Hi all, I'm hoping you can help me as the manufacturer of my new fireplace insert hasn't been very responsive. It's a new Osburn Matrix and it has a one-speed blower. It seems like a decent appliance but the blower is very loud. I'd like to try to use this fan speed adjuster. Would this work without damaging the blower motor?

Any advice would be appreciated! Thanks.

 

[marty319]

That's surprising to hear as I have never had an issue with sbi.they have always responded to emails and returned calls.what about your dealer?

 

[jetsam]

Hi all, I'm hoping you can help me as the manufacturer of my new fireplace insert hasn't been very responsive. It's a new Osburn Matrix and it has a one-speed blower. It seems like a decent appliance but the blower is very loud. I'd like to try to use this fan speed adjuster. Would this work without damaging the blower motor?

Any advice would be appreciated! Thanks.

You'll have to reach out to the manufacturer of the fan speed control and ask for a spec sheet or a circuit diagram. They don't link one off the product page.

In general I'd stay away from rheostats and and other types of resistive controls, but I'd be open to putting a PWM controller on most fan motors.

I guess you could also buy one, pop it open, and see what's in there before using it! If it's a switch and a bunch of power resistors, send it back.

 

[michoujordan76]

That's surprising to hear as I have never had an issue with sbi.they have always responded to emails and returned calls.what about your dealer?

They initially answered with this:
"Hello,
Unfortunately no other blower is approved to function with this fireplace and can not be changed. If changed this will void your warranty.
Regards,"

I sent a follow-up question but they haven't replied. I had a local sweep instal it and he'll be back in a few weeks with the surround trim. I could ask him his opinion then.

 

[jetsam]

They initially answered with this:
"Hello,
Unfortunately no other blower is approved to function with this fireplace and can not be changed. If changed this will void your warranty.
Regards,"

I sent a follow-up question but they haven't replied. I had a local sweep instal it and he'll be back in a few weeks with the surround trim. I could ask him his opinion then.

No offense to sweeps, but they may not be trained to know the difference between a rheostat and a PWM controller.

A resistive controller is going to vary fan speed by lowering the input voltage, which could kill your fan.

 

[DBoon]

A resistive controller will lower the voltage to the motor but still deliver a pure sine wave. The resistor in the controller will consume the power the motor does not get and generate heat. The motor is not very likely to be damaged by a lower voltage sine wave (within reason).

A PWM controller (variable speed/frequency drive or control) uses pulse-width modulation (PWM) to lower the voltage or change the frequency of the applied voltage. A motor not designed for PWM voltage applications will likely suffer insulation failure early. It is pretty safe to assume that the average low-cost blower motor is not designed for PWM voltage.

 

[john26]

I have 2 inserts both have factory installed speed controllers they are both rheostats

 

[savageactor7]

We've had a rheostat blower since we got this stove and love it. In your particular case it would be better just to buy a new blower with one.

 

[jetsam]

A resistive controller will lower the voltage to the motor but still deliver a pure sine wave. The resistor in the controller will consume the power the motor does not get and generate heat. The motor is not very likely to be damaged by a lower voltage sine wave (within reason).

A PWM controller (variable speed/frequency drive or control) uses pulse-width modulation (PWM) to lower the voltage or change the frequency of the applied voltage. A motor not designed for PWM voltage applications will likely suffer insulation failure early. It is pretty safe to assume that the average low-cost blower motor is not designed for PWM voltage.

PWM stands for Pulse Width Modulation. There is no adjustment of the peak voltage.

Simple PWM can (counterintuitively) be hard on motor windings due to the rapid changes in voltage, but I'll take that over a motor being forced to run in brownout conditions any day.

All this said, back in the day pretty much all fan speed controls were rheostats, and the world kept spinning.

 

[DBoon]

A rheostat will work fine, it will just not be as efficient as a PWM control. A rheostat will be better for your average blower.

A PWM controller controls both voltage and speed. Voltage is controlled by the pulse widths and speed is controlled by the frequency of the sinusoidal modulation.